Flash-heat milk to destroy bacteria.

Existing commercial treatments for processing ultra-high temperature (UHT) milk create a cooked flavor that can detract from the product's fresh taste. But scientists at the Western Dairy Center (Utah State University, Department of Nutrition and Food Science, UMC 8700, Logan, UT 84322) are using electricity in a novel process for UHT milk.

By passing electrical current directly through pasteurized milk, they flash-heat milk to destroy virtually all bacteria present. The technique, known as "electroheating" and developed by researchers at Raztek Corp. (Sunnyvale, CA), creates a more appealing, fresher-tasting milk that has an extended shelf life.

In a series of taste trials, consumers preferred the taste of the electroheated milk to a commercial UHT-processed milk by a margin of 2 to 1. A panel of trained tasters also found electroheated milk to be sweeter and to have less bitter, oxidized and stale flavors than UHT-processed milk.

By passing an electrical current directly through the milk itself, scientists are able to reach UHT levels in a fraction of a second, rather than in minutes. This quicker heating process is key to producing a fresh-tasting milk product.

Although UHT-processed fluid milk is gaining favor in various parts of the world, Americans accustomed to the ready availability of fresh milk have been slow to accept it, in part because of its cooked flavor. UHT processes in commercial use rely on indirect heat exchange through a metal plate or the direct addition of steam into the milk.

Heat exchange is a time-consuming physical process that requires 1 minute to 2 minutes when indirect heating is used. The longer milk is exposed to high temperatures, the more cooked flavors develop in the end product. Direct heating with steam is quicker, but the added water has to be removed by vacuum evaporation during the cooling process.

Electroheating is believed to be regulatory-acceptable, which could be an advantage for commercial producers. While researchers are continuing to explore a variety of nonthermal ways to extend milk's shelf life, these experimental techniques carry a scientific burden of proof. Electroheating, on the other hand, creates heat sterilization temperatures identical to those of current UHT-processed milk. Therefore, electroheating could effectively meet milk regulatory and safety compliances while extending shelf life.

You may want to consider using UHT to pasteurize whole muscle meats as well. In the process, you expose whole muscle meats to ultra-high temperatures-greater than 800 C-in a gas-fired oven to destroy all vegetative pathogens on the surface of the product. Meat surfaces are denatured to a depth of 0.5 mm, giving the meat a cooked appearance. The balance of the muscle remains raw, with active native enzyme activity.

After UHT treatment, the raw meat can be aseptically packaged in a controlled atmosphere. Shelf life at 4.4 C is between 15 and 20 weeks. You can add grill marks to the surface of some cuts to improve eye appeal. You also could develop a charcoal flavor. The technology is applicable to whole muscle cuts of beef, pork, lamb, poultry and fish, among other products.

Extended storage at 4.4 C of UHT-treated meats improves tenderness due to the activity of the native enzymes. Top round beef roasts with initial shear values of 5 to 7 exhibited shear values of 2 to 3 after 12 weeks of storage at 4.4 C. When pasteurizing poultry, UHT processing turns breast meat a very appealing white color and enables it to retain its juiciness. It does the same for pork. UHT technology has received USDA approval. The developers have processed products in a USDA-approved plant.

Further information. On milk: Donald McMahon; phone: [phone]; fax: [phone]. On meats: Von Mendenhall; phone: [phone]; fax: [phone].